THE SOIL AS AN ASSET 235 



was unable to get a reaction of iodine in the 

 concentrated solution. This seems to prove 

 beyond doubt that plants actually do extract 

 iodine from sea water containing less than one 

 part iodine in 30,000,000. In much the same 

 way the gigantic submarine plant, kelp, ex- 

 tracts potash from sea water in enormous 

 quantities. It has recently been seriously pro- 

 posed that kelp will become an important 

 source of our future potash supply. 



In spite of the fact, however, that plants 

 can, and actually do, make use of their food in 

 these dilute solutions, a mere scientific demon- 

 stration is of no value to Jeremiah, the Farmer 

 of To-morrow unless it can be proved at the 

 same time that such dilute solutions are capa- 

 ble of producing crops in paying quantities. 



If the plant in either the test solution or in 

 actual field conditions merely sustains growth 

 the experiment is useless. If on the other 

 hand it can be shown that the normal rate of 

 solution of these supposedly insoluble minerals 

 is capable of producing bountiful crops then 

 the secret is of tremendous economic impor- 

 tance. 



The promulgators of the new hypothesis are 



